ohw 12-solutions

# ohw 12-solutions - Reilly (mar3978) ohw 12 turner (56725)...

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Reilly (mar3978) – ohw 12 – turner – (56725) 1 This print-out should have 17 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 (part 1 of 3) 10.0 points A total charge oF 9.7 mC passes through a cross-sectional area oF a nichrome wire in 3 . 4 s. a) What is the current in the wire? Correct answer: 0 . 00285294 A. Explanation: Let : Δ Q 1 = 9 . 7 mC and Δ t 1 = 3 . 4 s . I = Δ Q Δ t = 0 . 0097 C 3 . 4 s = 0 . 00285294 A . 002 (part 2 of 3) 10.0 points b) How many electrons pass through the cross-sectional area in 4.50 s? Correct answer: 8 . 0239 × 10 16 . Explanation: Let : q e = 1 . 6 × 10 19 C and Δ t 2 = 4 . 50 s . Δ Q = N q e N = Δ Q q e = I Δ t 2 q e = (0 . 00285294 A)(4 . 5 s) 1 . 6 × 10 19 C = 8 . 0239 × 10 16 . 003 (part 3 of 3) 10.0 points c) IF the number oF charges that pass through the cross-sectional area during the given time interval doubles, what is the resulting cur- rent? Correct answer: 0 . 00570588 A. Explanation: Let : Δ Q 2 = 2 Δ Q 1 . I = 2 Δ Q 1 Δ t 1 = 2 (0 . 0097 C) 3 . 4 s = 0 . 00570588 A . 004 10.0 points An electrician fnds that a 1 . 4 m length oF a certain type oF wire has a resistance oF 0 . 29 Ω. What is the total resistance oF the 139 m oF this wire he plans to use to wire a house? Correct answer: 28 . 7929 Ω. Explanation: Let : 1 = 1 . 4 m , 2 = 139 m , and R = 0 . 29 Ω . A 1 . 4 m length oF the wire has a resistance oF λ = R 1 , so the total resistance oF the wire is R tot = λ ℓ = R 1 = p 0 . 29 Ω 1 . 4 m P (139 m) = 28 . 7929 Ω . 005 (part 1 of 2) 10.0 points Suppose that a uniForm wire oF resistance R is stretched uniFormly to N times its original length. Assume the total volume oF the wire re- mains the same, and the volume is given by the product oF the cross sectional area and the length. Denote the original area by A and the area aFter the stretch by A .

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Reilly (mar3978) – ohw 12 – turner – (56725) 2 The ratio A A is 1. A A = 1 N 2 2. A A = N 3. A A = 1 N 4. A A = N 3 / 2 5. A A = N 2 6. A A = 1 N correct 7. A
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## This note was uploaded on 11/30/2010 for the course PHY 60230 taught by Professor Turner,j during the Spring '10 term at University of Texas at Austin.

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ohw 12-solutions - Reilly (mar3978) ohw 12 turner (56725)...

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